Answer:
a) 0.9998
b) 0.9979
c) 0.7
d) 0.9155
Step-by-step explanation:
P( people who wear their ties tightly ) = 0.3
P( people who do not wear their ties tightly ) = 1 - 0.3 = 0.7
sample size ( n ) = 30
<em>Given that the events are independent and there are only two outcomes we will apply Binomial distribution </em>
<u>a) P( at least one tie is too tight ) </u>
P ( x ≥ 1 ) = 1 - P ( x < 1 ) = 1 - P ( x = 0 )
= 1 - 0.00002 = 0.9998 ( excel function: 1 - BINOMDIST(0,30,0.3,0) )
<u>b) P( more than two ties are too tight )</u>
P ( x > 2 ) = 1 - P ( x ≤ 2 ) = 1 - BINOMDIST(2, 30, 0.3, 1 )
= 1 - 0.002113178
= 0.9979
<u>c) P ( no tie is tight )</u>
P ( x = 0 ) = 0.7
<u>d) P( at least 18 ties are not too tight ) i.e. ( P = 0.7 )</u>
P ( x ≥ 18 ) = 1 - P( x ≤ 17 )
= 1 - BINOMDIST ( 17, 30, 0.7, 1 )
= 1 - 0.08447006
= 0.9155
